This invention relates to high frequency screening of electrical systems. The importants of screening against extraneous noise in an industrial environment is well recognised with the result that component design and layout aims at high efficiency screening which is quantified by a low transfer impedance across the conducting members forming the screen surrounding a sensitive circuit. The invention concerns preservation of this property where an otherwise continuous screen is interrupted for either connection to a further screen as in connections between cables and components or connection to a terminal screen structure such as between a component screen and a closure plate. Some aspects of design of mating faces at such interruptions are discussed in a paper entitled "Screened Coaxial Cable Connections for High Sensitivity Systems" by E. P. Fowler presented at an IEEE Symposium on Electromagnetic Compatibility at Montreux in May 1975.